Five laccase enzyme isoforms were isolated and purified to homogeneity from the cladodes of xerophytic Cereus pterogonus and Opuntia vulgaris plant species. Catalytic activity of all isoforms was enhanced 40 % by 1 mM Cu2+ and 1 mM Mn2+, whereas the activity was inhibited 100 % by 10 mM Fe2+. Enzyme was found stable in 4 M urea and exhibited inactivity of 50 % in 8 M urea concentration. Ethylenediaminetetraacetic acid and cysteine-HCl were able to completely inhibit the enzyme activity at 1 mM and 100 mu M, respectively. Preheated enzyme samples showed enhanced and stable catalytic activity in the presence of divalent cations over a period of 30 min compared with controls. In the presence of metal ions (1 mM Cu2+ and 1 mM Mn2+), the preheated enzyme forms (60-90 A degrees C) achieved 97 % of Malachite green and 98.75 % of Indigo blue (both at 2 %, w/v) dye decolorization in 12 h.